In the course of installing wire into conduit, an electrician generally uses a tool typically known as a fish tape. The fish tape can be used by electricians to route or pull electrical wiring through walls and the electrical conduit. Typically, fish tape is a narrow length of flexible steel that is coiled on a spool and packaged in a plastic case for storage and transportation. The fish tape is rigid enough to be pushed through the conduit, yet flexible enough to bend around corners or curves that may be inherent in a particular run of conduit. Wire may need to be used for long distances, and thus, it is typical to have fish tape of lengths of 25 feet, 50 feet, 100 feet, or more. One end of the fish tape, the proximal end, is usually anchored to a stationary or rotatable portion of a reel of spool to keep the end from coming loose. The other end, leading (or distal) end, of the fish tape is adapted in some way (e.g., hooked) to readily attach wire(s) to be pulled by the fish tape through the conduit.
In use, after the fish tape has been inserted through the conduit, the wire to be installed is affixed to the end of the fish tape and the fish tape is pulled back through the conduit to draw the wire with the fish tape. Once through, the wire is typically terminated at any necessary connection on each end and installation of the wire within the conduit is complete.
When installing wires, it is desirable to measure a length of a particular run of conduit and/or a location of an obstruction in the conduit in which the wire is to be installed. An inaccurate measurement or estimate may cause the installer to cut the wire too short, or too long, resulting in wasted scrap wire and therefore wasted money.
One way to measure the length of the run is to use measuring string. Here, the fish tape is first inserted at the proximal end of the run and fished to the distal end of the run. Next, a measuring string (and perhaps an accompanying pull string) is affixed to the leading end of the fish tape appearing at the distal end of the run. Then, the fish tape and the attached string(s) are pulled back through the conduit. When the leading end of the fish tape has been retrieved from the proximal end of the run, the installer can determine the length of the run via the measuring string. The wire(s) may (not necessarily) then be cut to the appropriate length. Finally, to install the wire(s) in the conduit, the wire(s) are then affixed to the leading end of the string(s) appearing at the proximal end of the run and are pulled back through the conduit. Once through, the wire is terminated as necessary.
Another way to measure the run is to first insert the fish tape at the proximal end of the run and to fish the fish tape to the distal end of the run. Once the leading end of the fish tape appears at the distal end of the run, the installer manually marks (perhaps with a piece of tape or a pen, etc.) the section of fish tape that is nearest to the proximal end of the run, pulls out the fish tape, and lays the fish tape on the ground. The distance between the leading end of the tape and the marked section on the tape represents the required length of wire. The wire(s) are then measured against the fish tape and may be cut to the appropriate lengths. In a next step, the fish tape is reinserted at the proximal end of the run and fished to the distal end of the run. Finally, to install the wire(s) in the conduit, the cut wire(s) are then affixed to the leading end of the fish tape appearing at the distal end of the run and are pulled back through the conduit.